This invention relates to an apparatus integrated in a carding machine or a roller card unit for forming a sliver from a fiber web. The apparatus has a roll assembly, formed of a doffer, a stripping roll and a crushing roll pair or, in the alternative, a shoving roll pair. The apparatus further has a web gathering device followed by a calender (pull-off) roll pair. In its outlet region the web gathering device densifies the web and discharges a sliver. The sliver exiting the device is introduced into the calender roll pair.
In practice, in the fiber batt processing industry, roller card units and carding machines are used which, for forming a fiber web, have a transitional guide plate (open web triangle), a standing roll pair and a downstream-arranged calender unit. It is a disadvantage of these known arrangements that the cross section of the produced sliver significantly deviates from a rectangular shape. It is also a drawback that the fiber material is not uniformly distributed over the sliver cross section. The thus-produced intermediate product (sliver) leads to irregularities during further processing to obtain the final product, such as a hygiene item.
German patent document 22 50 834 describes a transverse web gathering device which has a conveyor belt and a conveyor roll, followed by a sliver trumpet to form a sliver from a fiber web. The fiber web, after being densified in a closed zone, leaves the transverse gathering device and runs through a sliver trumpet and calender rolls and is thereafter deposited into a sliver can. The roll nip in the transverse gathering device is narrow and the inlet of the trumpet is at a substantial distance from the outlet of the transverse gathering device. The outlet of the trumpet has a circular cross section, and thus the exiting sliver assumes a circular cross section as well. The trumpet outlet is situated at a distance upstream of the bight defined by the calender roll pair. Such an apparatus is not adapted to form a sliver having a rectangularxe2x80x94particularly sharp-edgedxe2x80x94cross section. It is a further disadvantage of the known arrangement that because of the distances of the trumpet inlet from the transverse web gathering device, on the one hand, and the trumpet outlet from the calender nip, on the other hand, the processing of the fiber material having a significant amount of short fibers is not possible. Also, the above-noted relatively large distances do not allow a high delivery speed.
It is an object of the invention to provide an improved apparatus of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, produces an improved sliver having a rectangular cross section and which further permits a production rate higher than heretofore.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the fiber sliver producing apparatus includes an arrangement for making a running fiber web and a web gathering device which has a plurality of walls defining an inner space through which the fiber web runs in an advancing direction. The walls are stationary during operation of the apparatus. The web gathering device has a web gathering portion causing the running fiber web to converge and a web densifying portion, situated downstream of the web gathering portion as viewed in the advancing direction, for forming a running sliver from the web. The web densifying portion has an outlet opening of cross-sectionally rectangular outline and an opening width which is at least five times greater than the opening height. Upon discharge through the outlet opening, the sliver passes through cooperating rolls of a calender roll pair defining a bight in which the outlet opening of the web gathering device is disposed.
By virtue of the measures according to the invention a sliver having a rectangular cross section may be produced which has a more uniform fiber distribution and a significantly increased output speed (at least 100 m/min) compared to prior art arrangements. In particular, the processing of the fiber material with a higher short-fiber proportion is advantageously feasible.